1. Field of the Invention
This invention relates to pressurized fluid product dispensing apparatus. More particularly, it relates to apparatus for pressurized dispensing of fluid products, including very fine powders, in which the dispensing pressure is provided by the inherent contracting force of an expanded pressure unit.
2. The Prior Art
The use of pressure units, such as an elastomeric body, to contain a fluid product and to provide the fluid dispensing pressure is disclosed in the U.S. patents of Calvin L. Kain, entitled "CONTAINER FOR PRESSURE DISPENSING OF FLUID", No. 3,940,026, and "APPARATUS FOR PRESSURE DISPENSING OF FLUID" No. 4,121,737.
Both of these prior applications disclose bonding the upper end of the elastomeric pressure unit to the valve support to provide a fluid-tight connection therebetween. Also U.S. Pat. No. 4,121,737 shows the use of a liner inside the elastomeric pressure unit to contain the product and protect it from contamination by contact with the elastomeric pressure unit. However, the attachment of the liner requires additional sealing means.
While the fluid dispensing apparatus, as disclosed in such prior applications, are entirely satisfactory and functional, the use of bonded connections between the elastomeric pressure unit and the valve support, and the required use of additional sealing means when a liner is used, all increase the cost of production, provide the possibility for manufacturing defects and require detailed inspection procedures to assure that each bond is complete and fluid-tight. Since pressurized fluid dispensing apparatus are generally disposable, it is desirable to keep the manufacturing cost of the apparatus as low as possible. It is also desirable that such an apparatus be simple to manufacture and assemble to reduce the possibility of manufacturing defects.
The U.S. Pat. No. to Venus, et al 3,876,115 discloses analogous fluid dispensing apparatus utilizing dual nested pressure members formed of relatively thin-walled elastomeric material. In the Venus, et al apparatus, the pressure members are provided with upper sealing flanges which are trapped between upper and lower retaining members to provide a fluid seal. However, because of the relatively thin-walled material utilized for the pressure members, the upper and lower retaining members must be provided with mating grooves and projections for locking the pressure members into place and preventing their being pulled out of place when the unit is inflated.